With reference to FIGS. 1 and 2, an array substrate of a conventional TFT-LCD (Thin Film Transistor-Liquid Crystal Display) comprises: a gate line 11′ and a gate electrode 2′ formed on the base substrate 1′; a gate insulating layer 3′ formed on the gate line 11′ and the gate electrode 2′; an active layer 7′, a source electrode 4′ and a drain electrode 5′ formed on the gate insulating layer 3′; a passivation layer 8′ formed on the active layer 7′, the source electrode 4′ and the drain electrode 5′; a through hole 9′ formed in the passivation layer 8′; and a pixel electrode 6′ formed on the passivation layer 8′. The pixel electrode 6′ is connected to the drain electrode 5′ via the through hole 9′. This array substrate is widely adopted due to its good controllability and the like.
However, this array substrate has the following problems.
The through hole 9′ for connecting the pixel electrode 6′ and the drain electrode 5′ is within the pixel region of the array substrate, and the region for the through hole 9′ is opaque. Thereby, the aperture ratio of the array substrate is adversely influenced.
In the thin film transistor with top gate structure, the active layer may be undesirably irradiated by the light from a backlight. Accordingly, the thin film transistor with bottom gate structure is generally adopted in the array substrate. In the thin film transistor with the bottom gate structure, the source and the drain electrodes and the gate electrode are disposed on opposing sides of the active layer, as shown in FIG. 2. When the gate electrode 2′ is switched on, a current passage C′ is formed on the bottom side of the active layer 7′ so that the current passage C′ and the source and drain electrodes are separated by a region corresponding to the thickness of the active layer 7. Since the conductivity of the active layer 7′ is relatively low, the properties of the TFT may be reduced in the case that the current passes through the region separating the current passage C′ and the source and drain electrodes.